According to the results of a study published in Cancer Epidemiology, Biomarkers & Prevention, women with ductal carcinoma in situ (DCIS) that has high levels of the HER2 protein are several times more likely than other women with DCIS to have invasive breast cancer.

DCIS refers to a noninvasive, early stage of breast cancer. Abnormal cells are found in the lining of a breast duct but do not penetrate through the wall of the duct into surrounding breast tissue. In some cases, DCIS occurs in conjunction with invasive breast cancer. DCIS may also progress to invasive breast cancer if not treated, but it’s not currently possible to predict which cases will progress and which will not.

HER2 is a protein involved in cell growth. Cancers that overexpress (make too much of) this protein may grow and spread faster than other cancers, and many women with invasive HER2-positive breast cancer are treated with drugs such as Herceptin® (trastuzumab) that target HER2.

HER2 status is not routinely assessed in women with DCIS because it does not affect DCIS treatment decisions. It’s possible, however, that HER2 overexpression could help identify women with DCIS who are more likely to have invasive breast cancer. To explore this question, researchers at the University of Pennsylvania examined DCIS samples from 106 women.

37% of patients had DCIS that overexpressed HER2.

Based on final pathology, 21% of patients were found to have invasive breast cancer.

Patients with DCIS that overexpressed HER2 were more than six times more likely than other DCIS patients to have invasive cancer.

In a prepared statement, one of the researchers notes: “From a practical standpoint, if you know that a patient has a greater chance of invasive cancer when you’re doing a lumpectomy or mastectomy, then you might want to do a sentinel node biopsy, because there is a greater chance the cancer has spread to the lymph nodes.” He goes on to say, “If HER2 is associated with invasion or plays a role in the development of invasive disease, then maybe targeting it early can keep people from moving from DCIS to invasive cancer.”

Additional research on this question will improve our understanding of the biology and behavior of DCIS, and could eventually influence treatment decisions.